Dentists use composite filling material which cures under the influence of electromagnetic radiation in the wavelength range from approx. 380 nm to approx. 500 nm, especially in the violet/blue wavelength range from 405 nm to approx. 460 nm. While blue light is required to start and to drive the curing process of the filling material, blue light in the operating environment can interfere with the application of the filling material, as the blue light can significantly shorten the working time of the material due to premature curing.
Some dental lights offer a so-called “non-curing mode feature” in which blue light is excluded from the output of the non-curing mode. A second, or normal illumination mode, may provide white light including blue spectral output. Where light emitting diodes (LEDs) are used to provide the light source for such a dental light, multiple color LEDs (e.g. red, green and blue) generate the white light, and a non-curing mode is achieved by switching off or turning down the blue LED resulting in low quality light having a low color rendering index. Furthermore, systems using multiple color LEDs require frequent recalibration of the LED intensities over time to maintain the quality of white light in the normal mode.
Differences in lumen depreciation are typical in an LED system using RGB to produce white light. In particular, the intensity of each of the red, green and blue LED elements degrade at different rates, with the result that the proportion of each color in an RGB system tend to change over time. This results in undesirable or unpleasant color (e.g. off the black body curve) and/or a reduction in the quality of the white light. For example, a color rendering index (CRI) is a proxy for light quality, wherein a CRI of 100 is considered identical to natural lighting. Deviations in the lumen depreciation profiles of multi-color LED systems therefore lead to CRI values substantially below 100 unless expensive color correction schemes are employed to counteract the effects of the depreciation.